SY0-301 Question #798: Real Exam Question with Answer & Explanation

The correct answer is C: TCP 53. DNS (Domain Name System) operates on port 53 for both transport protocols. UDP 53 is used for standard queries because it is lightweight and fast. TCP 53 is used for responses larger than 512 bytes (e.g., DNSSEC records) and for zone transfers between DNS servers. Both must be op

Question

A security technician needs to open ports on a firewall to allow for domain name resolution. Which of the following ports should be opened? (Select TWO).

Options

ATCP 21
BTCP 23
CTCP 53
DUDP 23
EUDP 53

Explanation

DNS (Domain Name System) operates on port 53 for both transport protocols. UDP 53 is used for standard queries because it is lightweight and fast. TCP 53 is used for responses larger than 512 bytes (e.g., DNSSEC records) and for zone transfers between DNS servers. Both must be opened to ensure full DNS functionality. TCP 21 is FTP, and TCP/UDP 23 is Telnet - neither is related to DNS.

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